The invention relates to a device for individually transferring flat objects from an entry conveyor on which said objects travel in series edge-on in a first direction, into buckets of an exit conveyor, the device comprising an intermediate conveyor arranged in the continuation of the entry conveyor above the exit conveyor and equipped with receptacles which, over at least part of their path, can move in a second direction perpendicular to said first direction, each flat object leaving the entry conveyor being injected edge-on into a receptacle of the intermediate conveyor which comes up to face the exit of the entry conveyor so as to be transferred edge-on into a bucket of the exit conveyor.
A device of this kind is more specifically intended for a postal sorting machine and is already known from patent document EP-0608161. In this known device, the entry conveyor comprises two motorized belts moved at constant speed and between which the envelopes, arranged edge-on and in series, are gripped, and each envelope leaving the entry conveyor is injected directly edge-on into a receptacle of the intermediate conveyor. The speed at which the envelopes are ejected at exit from the entry conveyor is about 3 meters per second. Given this high speed level, the envelopes injected into the receptacles of the intermediate conveyor violently strike the bottom of these receptacles, which means they may become damaged under the effect of the impact.
The purpose of the invention is to overcome this drawback.
To this end, the subject of the invention is a transfer device as defined hereinabove, wherein an injection system is disposed at the exit end of the entry conveyor and designed to accelerate and then retard the movement of each flat object in said first direction before injecting it into a receptacle of the intermediate convey by using an injection system, as known from the patent document EP 0574710, which is designed to accelerate and after decelerate a product between the end of a feed conveyor and a distribution point of the product. With this arrangement, the flat objects can be injected into the receptables of the intermediate conveyor at a lower speed by comparison with the speed at which they exit the entry conveyor, thus making it possible to reduce the violence of the impact.
The injection system comprising two parallel rows of several elastically deformable elastomer wheels with stationary rotation spindles, between which wheels each flat object is gripped, these two rows of wheels comprising wheels arranged on the same side as the entry conveyor and rotated at constant speed with the possibility of being placed freely at overspeed and wheels arranged on the same side as the intermediate conveyor, which are rotated at variable speed. Each flat object moved in the entry conveyor at a certain speed is taken up firstly by the wheels rotated at a constant speed that corresponds to the speed at which the flat object moves as it leaves the entry conveyor. As soon as the flat object is released from the entry conveyor, the wheels rotated at variable speed take up this flat object and can accelerate its movement to be able to inject it into a receptacle of the entry conveyor having retarded its movement. Because the wheels rotated at constant speed can be freely set to an overspeed (that is to say a freewheel effect), they do not oppose the accelerating of the movement of the flat object between the two rows of wheels. It must be understood that the phase of retarding the movement of the flat object has to coincide with the instant when the flat object is no longer gripped between the wheels which are rotated at constant speed.
According to yet another particular embodiment of the device according to the invention, a means is provided for determining the length of each flat object in said first direction and the speed of rotation of the wheels driven at variable speed is regulated according to said length determination, which makes it possible to broaden the range of flat objects that can be transferred to the buckets of the exit conveyor.
According to yet another embodiment of the device according to the invention, each wheel comprises a hub and an annular tread strip made of elastomer which are connected together by elastomer circular-arc-shaped fins, the points of attachment of each fin to the hub and to the tread strip of the wheel being aligned on a radius of the wheel which makes it possible to make the elastomer work over the entire length of the fins without creating any stress concentration zones. Such wheels are well suited to tolerating significant variations in thickness of the flat objects. They have far better positional-return dynamics than simple pulleys mounted on pivoting arms returned by springs. Because they are mounted on stationary rotation spindles, the structure of the transfer device is simplified and requires little maintenance.
According to yet another embodiment of the device according to the invention, the receptacles of the intermediate conveyor are grooves which run in a third direction perpendicular to the first and second directions and a flat support is provided in the continuation of the entry conveyor between the intermediate conveyor and the exit conveyor so that a flat object injected into a groove of the intermediate conveyor is kept edge-on and moved along standing on its edge in said second direction as far as one end of said flat support to then fall under gravity into a bucket of the exit conveyor. This flat support may be a stationary plate or may alternatively be a motorized endless belt. This arrangement plays a part in simplifying the structure of the intermediate conveyor by avoiding providing receptacles with a mobile flap. Using this arrangement, each flat object injected into a groove of the intermediate conveyor can be positioned correctly edge-on in an inclined position before dropping under gravity into a bucket of the exit conveyor, thus making it possible to obtain good positioning of the flat object edge-on in the bucket.